1. Field of the Invention
The present invention relates to a chronograph timepiece having a time indicating function and a time measuring function.
2. Background Art
Conventionally, there has been developed a chronograph timepiece in which a plurality of driving motors are mounted to respectively drive a plurality of indicator hands to perform time information indication as a basic function, and which is further endowed with a chronograph function to perform time measurement, wherein the driving of each indicator hand is effected electrically by the driving motors; and the zero-restoring of the chronograph hands is effected by a mechanical mechanism such as hearts (See, for example, JP-A-2005-3493).
As in the case of the chronograph timepiece disclosed in JP-A-2005-3493, in a chronograph timepiece in which the chronograph hands are electrically drive-controlled and mechanically zero-restoring-controlled, when, for example, in the reset state, the heart of an arbor (shaft) with a chronograph hand is mechanically maintained in the zero-restored state by a hammer.
Thus, in the above-mentioned chronograph timepiece, when giving a chronograph operation start instruction by depressing a start button, a lever related to zero-restoring is rotated or the like to displace the hammer, thereby permitting the rotation of a chronograph arbor, which is integral with the heart (the releasing of zero-restoring control); then, it is necessary to output a motor rotation drive signal for starting the movement of a chronograph hand in response to the depression of the start button (hand movement control start).
Actually, however, the requisite time for the releasing of zero-restoring control is not strictly fixed; in particular, it is a mechanical control and involves variation in the related components; further, if, in order to minimize the cost, an attempt is made to render the structure as simple as possible, the variation is likely to increase, so that variation in individual products is not always small.
On the other hand, if the releasing of the zero-restoring control has not been completed yet at the point in time when the motor rotation drive signal for the hand movement control start is output, an accurate chronograph operation cannot be executed.
To avoid this problem, conventionally, it has been necessary to design and produce the mechanical system such that the delay in the releasing of zero-restoring control is reliably made shorter than the time measurement cycle of the chronograph timepiece (e.g., 1/100 seconds) taking the variation into consideration. Here, if allowance is to be made for variation, there is nothing for it but to prepare a mechanical system which is more expensive than the one which is actually required in many cases.
In JP-A-2005-3493 also, there is made a proposal regarding the necessity to match the timing of electrical drive control and the timing of mechanical stop control or the like with each other, which necessity is a problem inherent in a system in which such electrical and mechanical controls are combined with each other. More specifically, JP-A-2005-3493 proposes, for example, a technique in which, in order to prevent the mechanical stop control or the like from being started although the rotation drive signal for the motor is still being output, the mechanical structure is modified so as to control the timing with which the zero-restoring control or the like is started. However, this modification proposed in JP-A-2005-3493 neither discloses nor suggests a technique leading to the solution of the above-mentioned problem involved when starting the chronograph operation in a chronograph timepiece in the zero-restored (reset) state.